Ron Dodson, KA4MAP
While we like to think that we live in a region where such incidents are unlikely, it must be realized that we do have a risk for WMD events anywhere and that they have already occurred in the past. Incidents involving bomb scares and even pipe bombs, supposedly contaminated mail scares, and others have occurred in this region in recent years. Individuals and groups often perform these acts for publicity or to gain an objective known only to them. Recent events have also led us to expect the use of chemical and biological weapons as well as the use of nuclear "dirty bombs" which can contaminate areas with radioactivity and can be of a relatively small size unlike atomic bombs of yesteryear. Purchases of plastic sheeting and duct tape from department stores of late also reflect the fact that people are starting to get the message about planning for shelter-in-place options in case of chemical weapons releases. Let’s discuss a few points to help
you stay safe if you find you are in an area where a suspected event is taking place.
Let's say you are shopping or driving along and need to stop and use a pay phone.
Perhaps you see a device or segment of PVC pipe next to the phone. Do you assume it is a prank and use the phone anyway? What if you are at a building where several people suddenly become ill or collapse, what should you do? In our first example, the telephone, there is obviously something wrong. Don't bet on it being a 'dud'. Back off, keep others away and summon the authorities. Be mindful that radio waves may detonate the device.
Our second example brings to mind an incident that I personally witnessed many years ago. The workers in a store were all suddenly stricken with a violent headache and blurred vision. I responded with several others to the scene and in spite of the comments made by others, and myself that the initial entry team should wear breathing apparatus, the crew walked in with no protection and sure enough, in 5 minutes time, THEY were now victims. Turned out that a chemical was leaking in the store, which created the problem. The second crew in, who wore SCBA’s, later found it. The moral of this story is: “Without proper protection, do not enter a situation without knowing what you are walking into.”
Watch for indicators at any possible haz-mat and/or WMD locations.
· Look for physical indications and outward warning signs.
· Unusual smoke, odors, vapor clouds.
· Dead animals or vegetation.
· Mass Casualties may or may not show outward signs of trauma.
· Victims with breathing difficulties. May or may not have blistered, or reddening skin and eye irritations etc.
For the untrained: do not approach, touch or examine devices, debris or victims. Stay upwind at a reasonable distance and summon aid. If you suspect that you may be contaminated, do not leave the area and go home. If you are, this would only endanger others and your families. Alert responders that you may be contaminated and follow through with any requested procedures until cleared to go. Be mindful that many incidents are 'staged' to draw in responders for a later release of a secondary device or 'booby trap'. The true targets may well be the responders and the initial victims may be considered only as 'collateral damage' by the perpetrator(s). Secondary devices may be as bad or worse than the initial incident! People who do these types of things do not think
like the average person on the street. The whole objective may be to 'take out' as many people as possible and by drawing in several responders and the inevitable gawkers close to a location; they may indeed have worse surprises. Stay out and let those with more training do the work. Lastly, if you receive an EAS warning to "shelter-in-place" for a chemical release, would you know what to do and do you have the right materials handy to do it with? If advised to "shelter-in place", immediately turn off all sources of outside ventilation and close all windows and doors. Keep your portable radio with you. Move to a 'safe room' in your home or work place. (When planning ahead for a safe room, try to locate one with at least ten feet of floor space per person to allow for adequate air space and preferably without windows.) Seal around the doors, vents and any windows with plastic sheeting (this can be pre-measured and cut to fit and marked well beforehand) and duct tape. Stay there until the all clear is given. In all likelihood, the chemical cloud will soon pass over and dissipate. Chemical agents do not linger long in the open air. A few
hours (2-5) will likely be adequate for the winds to blow them away. After the all clear is given, open windows and doors and allow fresh air to remove any residual chemical vapors. If you are outdoors when an alert is given and you have no available shelter, try to stay upwind and move away from the affected area. Listen for and follow any other EAS instructions you receive over your portable receiver. Lastly, Consider any possible WMD site as a crime scene! Anyone who has ever watched a TV detective show or two has at least a minimal idea of the need for scene integrity and evidence preservation. If an event has occurred and you are not in the area, do not rush to the scene! As amateur radio operators involved in ARES and RACES efforts we may be asked to help with communications during the course of the event, however, never take it upon yourself to go to a possible WMD scene just to see what you can find out. This is not only foolhardy; it can be deadly! If you are requested to activate by EM or another served agency, do as they ask to the extent of your training. Do not put yourself into locations in which you are not asked, equipped and cleared to enter.
Source: Kentucky Amateur Radio Web Site – www.kyham.net
Tuesday, June 12, 2007
Propagation and EMCOMM
An EM advanced studies training module - by D. W. Thorne, K6SOJ
EMCOMM.org
A few years ago I was involved in a Search and Rescue operation in extremely rugged country in the far NW corner of California. The primary search area consisted of two very deep and steep canyons that are separated by a 2,000 ft. ridge. Before the search was over about a dozen SAR units from as far away as 300 miles were called in to assist. There was no cell phone coverage and only one Sheriff's Department repeater was accessible. The IC (who was from an adjacent county) said the local Sheriff wanted to keep their SO frequency clear of the SAR traffic and asked that it be used (by SAR) for emergency traffic only.Around 2200 local time, one other emcomm volunteer (a trainee) and myself arrived at the SAR CP/base camp positioned in a deep canyon and we were asked immediately to establish contact with the Sheriff's Office the IC's home county. My first thought was about setting up a NVIS* antenna, and establishing an HF link either on 40 or 75 meters with one of several HF stations that had been previously alerted and were monitoring some previously designated frequencies and that could relay traffic to and from the Sheriff's Dispatch Center via telephone.
I knew there was a VHF amateur repeater located on a mountain top about 20 miles to the north...in another state! I thought, why not give it try? I switched to the repeater frequency, keyed the mic, heard the identifier, and then identified myself. Immediately, I heard a familiar voice reply...it was my wife! She was at our home station over 125 miles away, but by using out tower mounted 13 element Yagi she had solid contact with the repeater. Needless to say, the IC, who was watching, was very impressed!The search went on for about a week before finally being called off. The missing person (or his remains) were never found. Most of the searchers were non-hams, so all tactical communications were on VHF public service simplex frequencies (NASAR, CLEMARS, etc.). By stationing a radio relay team (the young trainee and myself) on the ridge that separated the two deep canyons, effective communications were maintained. Every message between the two canyons was through our relay.
A portable repeater may have worked, but there are very few (if any) used by public service agencies and there are very few "spare" public service "frequency pairs" available for portable/field operations. Plus mutual aid responders may not be able to program the radios to an "new" pair. Frequencies such as NASAR, CLEMARS, NALEMARS and other SOA (scene of action) simplex frequencies should be in all SAR transceivers.(NOTE: Typical amateur radio gear is not FCC "type accepted" transmitting on PS channels. Listen only. Hams who are active in SAR, fire, EMS, or other public service, should consider buying commercial radio gear that can be legally operated on both public safety and amateur services.)Most local amateur emcomm (and nearly all public service communications) are handled on VHF, UHF, or higher frequencies. Which are line-of-sight whether direct or via a repeater (if available).One of the great advantages that we as radio amateur have is that we have a wider range of frequencies and modes option that just about anyone! With all the new emcomm volunteers now entering the world of HF, it is advantageous to know some basic and practical aspects of HF radio propagation.40 and 80 meters are the "Workhorse Bands" for Regional Emcomm:
While most local or tactical emcomm can easily be handled on VHF or UHF frequencies, most regional traffic (50-300 or more miles) is handled on the 40 or 75-80 meter bands. (The 160 meter band and the 60 meter band should not be ruled out, but by and large the 40 and 80 meter bands are the workhorse bands most used for emcomm networks.
I am not a physicist are these comments an attempt to explain and define all the intricacies and nuances of HF radio signal propagation. There are many excellent books available that can adequately explain that area of science that is wrought with multiples and rarely understood variables. As one ham friend of mine says, "It's all Voodoo!"
The SEA and the SUNMost of us who have studied the basics of radio know that the earth is surrounded by layers of ionized particles. The ionosphere is in a constant state of flux. It is affected primarily by the sun, and it varies immensely with the time of day, the time of year, the solar cycle, geomagnetic storms, and other factors. The ocean tides on the earth are influenced by the gravitational pull of the sun and the moon and to a small degree, the other planets, and is compounded by the winds. The ionosphere (envision a canopy above the earth), is ever expanding, contracting, fluctuating in the amount of ionization level, and possibly other factors that scientists may not have even discovered.
The D layer (closest to the earth) is only a factor present during the daylight hours and is responsible for the absorbing most MW and HF radio signals. This is why MW BCB signals do not propagate (over any great distance) during daylight hours. Then there is "sporadic E", which some liken to clouds of ions which come and go with the seasons often only lasting a few minutes or hours. Radio hams who enjoy the six meter band (50-54 MHz) love it when the "E layer comes to life!" The most commonly relied upon layer for HF radio is the highest...the F layer. To further confuse the issue, the F layer divides into two levels during the daytime. F1 and F-2. One or the other will refract (bounce a signal back to earth) from a point of refraction depending upon: 1) the frequency; and 2) the angle at which a given signal hits that refraction point.Most of us knowledgeable hams who want to be able to maximize their ability to communicate by bouncing radio signals off the ionosphere, have learned by experience what works and what doesn't work. Often by much trial and error. (This is what is known as experience!) They have learned and also realize that what works today, may not work tomorrow, but it may work again the day-after-tomorrow. Even at the same time and on the same frequency! In fact...what works now, may not work five minutes from now!
Most of us have played pool or billiards. The object in those games is to bounce (or ricochet') a ball off of the opposite bumper. The more direct, or acute the angle that a ball hits the bumper, the closer it will return to it starting point. (E.g. - the side pocket near to you.) If you "glance the ball" off the bumper at an obtuse angle, it will "land" farther way from the starting point. (Hopefully, in the corner pocket.)
Radio signals behave in much the same way. Where they go, depends (in part) at what angle they are directed towards the ionosphere. NVIS (near vertical) go up, and down, land closer to the transmitting station, and may not interfere with distant stations. Low angle (aimed at the horizon) will land a long, long way away, but may not be heard by who you want to talk to.
Now, if the ionosphere was a straight edged surface like the bumper of a billiard table, it would be easier to calculate just where a signal might "bounce to" or land. (This is actually done using solid passive reflectors on mountains for micro wave communications.) But the ionosphere is curved and it consistently varies in thickness. Imagine that you are playing pool on a circular table! Imagine also the cushion is constantly changing in its softness. Now imagine that the table is constantly changing it's circumference. (Like the iris of the human eye or a camera.) That would make for a very challenging game of pool!
The ionosphere is constantly changing in all of these physical characteristics. Therefore, so does the refraction point (distance above the earth) vary for any given frequency. And...just as in billiards...the angle at which a signal "hits" that refraction point will determine how far it will "skip" or return to earth. To further complicate tings, the layer varies in thickness and intensity. If it didn't, the radio signals would be very specific as to where they land. When propagation is marginal, signal paths may actually be very selective. When band conditions are is optimal, signals on many frequencies may propagate well and be received over a wide footprint. This is often called signal scatter.
A few generalities to keep in mind:
1. 40 meters usually provides a better signal path during daylight hours for communications in the 100 to 800 mile range.2. 75-80 meters is usually better during daylight hours for communications in the 30-200 mile range.3. During daylight hours, when the MUF* is below 7 MHz, or when the 40 meter band "goes long", 75 meters may work.
4. 75-80 meters is usually better during nighttime hours. (40 meters tends to "go long" at night.)5. On 160, 80/75, and 40 meters, lower (30 ft. or less) horizontal antennas (NVIS**) are usually better for closer ranges.
6. Normally, the higher any antenna is (above ground) the lower the angle of radiation. (Good for DX...but not as good for NVIS.)
7. A vertical antenna has low angle of radiation, and probably will not get your signal "up and out" of a deep canyon or over another obstruction.
*MUF = Maximum Useable Frequency
** NVIS = Near Vertical Incident Signal http://www.emcomm.org/antenna/nvis.htm
EMCOMM.org
A few years ago I was involved in a Search and Rescue operation in extremely rugged country in the far NW corner of California. The primary search area consisted of two very deep and steep canyons that are separated by a 2,000 ft. ridge. Before the search was over about a dozen SAR units from as far away as 300 miles were called in to assist. There was no cell phone coverage and only one Sheriff's Department repeater was accessible. The IC (who was from an adjacent county) said the local Sheriff wanted to keep their SO frequency clear of the SAR traffic and asked that it be used (by SAR) for emergency traffic only.Around 2200 local time, one other emcomm volunteer (a trainee) and myself arrived at the SAR CP/base camp positioned in a deep canyon and we were asked immediately to establish contact with the Sheriff's Office the IC's home county. My first thought was about setting up a NVIS* antenna, and establishing an HF link either on 40 or 75 meters with one of several HF stations that had been previously alerted and were monitoring some previously designated frequencies and that could relay traffic to and from the Sheriff's Dispatch Center via telephone.
I knew there was a VHF amateur repeater located on a mountain top about 20 miles to the north...in another state! I thought, why not give it try? I switched to the repeater frequency, keyed the mic, heard the identifier, and then identified myself. Immediately, I heard a familiar voice reply...it was my wife! She was at our home station over 125 miles away, but by using out tower mounted 13 element Yagi she had solid contact with the repeater. Needless to say, the IC, who was watching, was very impressed!The search went on for about a week before finally being called off. The missing person (or his remains) were never found. Most of the searchers were non-hams, so all tactical communications were on VHF public service simplex frequencies (NASAR, CLEMARS, etc.). By stationing a radio relay team (the young trainee and myself) on the ridge that separated the two deep canyons, effective communications were maintained. Every message between the two canyons was through our relay.
A portable repeater may have worked, but there are very few (if any) used by public service agencies and there are very few "spare" public service "frequency pairs" available for portable/field operations. Plus mutual aid responders may not be able to program the radios to an "new" pair. Frequencies such as NASAR, CLEMARS, NALEMARS and other SOA (scene of action) simplex frequencies should be in all SAR transceivers.(NOTE: Typical amateur radio gear is not FCC "type accepted" transmitting on PS channels. Listen only. Hams who are active in SAR, fire, EMS, or other public service, should consider buying commercial radio gear that can be legally operated on both public safety and amateur services.)Most local amateur emcomm (and nearly all public service communications) are handled on VHF, UHF, or higher frequencies. Which are line-of-sight whether direct or via a repeater (if available).One of the great advantages that we as radio amateur have is that we have a wider range of frequencies and modes option that just about anyone! With all the new emcomm volunteers now entering the world of HF, it is advantageous to know some basic and practical aspects of HF radio propagation.40 and 80 meters are the "Workhorse Bands" for Regional Emcomm:
While most local or tactical emcomm can easily be handled on VHF or UHF frequencies, most regional traffic (50-300 or more miles) is handled on the 40 or 75-80 meter bands. (The 160 meter band and the 60 meter band should not be ruled out, but by and large the 40 and 80 meter bands are the workhorse bands most used for emcomm networks.
I am not a physicist are these comments an attempt to explain and define all the intricacies and nuances of HF radio signal propagation. There are many excellent books available that can adequately explain that area of science that is wrought with multiples and rarely understood variables. As one ham friend of mine says, "It's all Voodoo!"
The SEA and the SUNMost of us who have studied the basics of radio know that the earth is surrounded by layers of ionized particles. The ionosphere is in a constant state of flux. It is affected primarily by the sun, and it varies immensely with the time of day, the time of year, the solar cycle, geomagnetic storms, and other factors. The ocean tides on the earth are influenced by the gravitational pull of the sun and the moon and to a small degree, the other planets, and is compounded by the winds. The ionosphere (envision a canopy above the earth), is ever expanding, contracting, fluctuating in the amount of ionization level, and possibly other factors that scientists may not have even discovered.
The D layer (closest to the earth) is only a factor present during the daylight hours and is responsible for the absorbing most MW and HF radio signals. This is why MW BCB signals do not propagate (over any great distance) during daylight hours. Then there is "sporadic E", which some liken to clouds of ions which come and go with the seasons often only lasting a few minutes or hours. Radio hams who enjoy the six meter band (50-54 MHz) love it when the "E layer comes to life!" The most commonly relied upon layer for HF radio is the highest...the F layer. To further confuse the issue, the F layer divides into two levels during the daytime. F1 and F-2. One or the other will refract (bounce a signal back to earth) from a point of refraction depending upon: 1) the frequency; and 2) the angle at which a given signal hits that refraction point.Most of us knowledgeable hams who want to be able to maximize their ability to communicate by bouncing radio signals off the ionosphere, have learned by experience what works and what doesn't work. Often by much trial and error. (This is what is known as experience!) They have learned and also realize that what works today, may not work tomorrow, but it may work again the day-after-tomorrow. Even at the same time and on the same frequency! In fact...what works now, may not work five minutes from now!
Most of us have played pool or billiards. The object in those games is to bounce (or ricochet') a ball off of the opposite bumper. The more direct, or acute the angle that a ball hits the bumper, the closer it will return to it starting point. (E.g. - the side pocket near to you.) If you "glance the ball" off the bumper at an obtuse angle, it will "land" farther way from the starting point. (Hopefully, in the corner pocket.)
Radio signals behave in much the same way. Where they go, depends (in part) at what angle they are directed towards the ionosphere. NVIS (near vertical) go up, and down, land closer to the transmitting station, and may not interfere with distant stations. Low angle (aimed at the horizon) will land a long, long way away, but may not be heard by who you want to talk to.
Now, if the ionosphere was a straight edged surface like the bumper of a billiard table, it would be easier to calculate just where a signal might "bounce to" or land. (This is actually done using solid passive reflectors on mountains for micro wave communications.) But the ionosphere is curved and it consistently varies in thickness. Imagine that you are playing pool on a circular table! Imagine also the cushion is constantly changing in its softness. Now imagine that the table is constantly changing it's circumference. (Like the iris of the human eye or a camera.) That would make for a very challenging game of pool!
The ionosphere is constantly changing in all of these physical characteristics. Therefore, so does the refraction point (distance above the earth) vary for any given frequency. And...just as in billiards...the angle at which a signal "hits" that refraction point will determine how far it will "skip" or return to earth. To further complicate tings, the layer varies in thickness and intensity. If it didn't, the radio signals would be very specific as to where they land. When propagation is marginal, signal paths may actually be very selective. When band conditions are is optimal, signals on many frequencies may propagate well and be received over a wide footprint. This is often called signal scatter.
A few generalities to keep in mind:
1. 40 meters usually provides a better signal path during daylight hours for communications in the 100 to 800 mile range.2. 75-80 meters is usually better during daylight hours for communications in the 30-200 mile range.3. During daylight hours, when the MUF* is below 7 MHz, or when the 40 meter band "goes long", 75 meters may work.
4. 75-80 meters is usually better during nighttime hours. (40 meters tends to "go long" at night.)5. On 160, 80/75, and 40 meters, lower (30 ft. or less) horizontal antennas (NVIS**) are usually better for closer ranges.
6. Normally, the higher any antenna is (above ground) the lower the angle of radiation. (Good for DX...but not as good for NVIS.)
7. A vertical antenna has low angle of radiation, and probably will not get your signal "up and out" of a deep canyon or over another obstruction.
*MUF = Maximum Useable Frequency
** NVIS = Near Vertical Incident Signal http://www.emcomm.org/antenna/nvis.htm
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